SELECTIONS - Introduction to Java Programming: Comprehensive Version - page 89

3.8 Case Study: Computing Body Mass Index
You can use nested if statements to write a program that interprets body mass index.

Key
Point

Body Mass Index (BMI) is a measure of health based on height and weight. It can be cal-
culated by taking your weight in kilograms and dividing it by the square of your height in
meters. The interpretation of BMI for people 20 years or older is as follows:

BMI Interpretation

BMI < 18.5 Underweight

18.5 ≤ BMI < 25.0 Normal

25.0 ≤ BMI < 30.0 Overweight

30.0 ≤ BMI Obese

Write a program that prompts the user to enter a weight in pounds and height in inches and
displays the BMI. Note that one pound is 0.45359237 kilograms and one inch is 0.0254
meters. Listing 3.4 gives the program.

L ISTING 3.4

ComputeAndInterpretBMI.java
1 import java.util.Scanner;
2
3 public class ComputeAndInterpretBMI {
4 public static void main(String[] args) {
5 Scanner input = new Scanner(System.in);
6
7 // Prompt the user to enter weight in pounds
8 System.out.print( "Enter weight in pounds: " );
9 double weight = input.nextDouble(); input weight

10
11 // Prompt the user to enter height in inches
12 System.out.print( "Enter height in inches: " );
13 double height = input.nextDouble(); input height

14
15

final double KILOGRAMS_PER_POUND = 0.45359237 ; // Constant

16 final double METERS_PER_INCH = 0.0254 ; // Constant

17
18 // Compute BMI
19 double weightInKilograms = weight * KILOGRAMS_PER_POUND;
20 double heightInMeters = height * METERS_PER_INCH;
21 double bmi = weightInKilograms /
22 (heightInMeters * heightInMeters);
23
24 // Display result
25 System.out.println( "BMI is " + bmi);
26 if (bmi < 18.5 )
27 System.out.println( "Underweight" );
28 else if (bmi < 25 )
29 System.out.println( "Normal" );
30 else if (bmi < 30 )
31 System.out.println( "Overweight" );
32 else
33 System.out.println( "Obese" );
34 }
35 }

compute bmi

display output